The majority of γδ peripheral blood lymphocytes (PBLs) in human adults express T-cell receptors (TCRs) comprising Vγ9 and Vδ2 regions. Vγ9Vδ2 T cells can react against a wide array of pathogens and tumour cells. This broad reactivity is understood to be conferred by phosphoantigens which are able to specifically activate this T-cell subset in a TCR dependent fashion. The broad antimicrobial and anti-tumour reactivity of Vγ9Vδ2 T-cells suggest a direct involvement in immune control of cancers and infections. In addition to fighting disease, in some diseases or medical treatment Vγ9Vδ2 T cells may be overstimulated or inadvertently activated.
Hence, agents that can activate Vγ9Vδ2 T cells can be useful in the treatment of infections or cancer as these may promote Vγ9Vδ2 T cell reactivity towards the pathogen or infected cells or cancer. Furthermore, agents that block activation of Vγ9Vδ2 T cells may be useful in diseases or medical treatment where it is advantageous to reduce Vγ9Vδ2 T cell activation, i.e. wherein Vγ9Vδ2 T cells are overstimulated or inadvertently activated. Finally, agents that can bind a Vγ9Vδ2 T cell, but do not have an effect on (phosphoantigen) activation of Vγ9Vδ2 T cells are useful for labelling cells, for example for selecting or identifying Vγ9Vδ2 T cells. Hence, there is a need in the art to provide for agents that can bind to Vγ9Vδ2 T cells, and for agents that can block phosphoantigen activation of Vγ9Vδ2 T cells or can activate Vγ9Vδ2 T cells.